Torque shop: Wheels meant for a different make or model may not fit

Why can’t I use BMW wheels on a Honda?

The short answer to this is that wheels meant for a different make or model may not fit and, hence, will be impossible to mount on your car.

Many cars use wheels with five bolts, while others use four bolts or even six. Besides this, there are dimensional differences on wheels, even when comparing two makes of wheels with the same bolt-count.

The bolt-hole centres are spaced equally in a formation that guarantees the wheel will be in the dead-centre of the hub when mounted.

The age-old methodology of achieving this geometrical accuracy is to first scribe a circle with the same centre as the wheel itself. The bolt centres are then marked, equally spaced on the circumference, for drilling. The equal space between holes is called the “pitch”, while the circumference is referred to as “pitch circle”.

In engineering parlance, the term “pitch circle diameter” (PCD) is a specification used to define the location of a series of equally spaced holes, pins or gear-teeth relative to the centre of a rotating element.

There are a few commonly used PCDs within the automotive industry for passenger cars. You may find a European car that has the same PCD as a model from an Asian manufacturer, but that still does not mean the wheels are interchangeable.

The other important wheel specification is einpresstiefe, or ET (German for offset). If you have ever seen a car with tyres that seem to protrude out of the wheel arches, this is because the wheels of incorrect offset have been fitted.

Wheel offset varies widely within the industry between manufacturers and models from the same brand. It is an important parameter in the brake and suspension design. Deviating from the specification by more than 10mm could cause problems with the way the car handles.